Engine Ticking

[Dmod81]

All - need your help. My engine has developed a tick. I drove it on Sunday - embarrassingly I did hit the rev limiter. There were no issues when I parked it. Today, when I started the car, I heard the tick. Video is here: https://youtu.be/jiUyyVhvMvk

It does increase with engine rpm, although there gets to be a point where I can't hear it due to exhaust noise. The car does seem to shake a bit. Oil is good and oil pressure is good. I attached my timing light to all of the plug wires, and got only very intermittent flashing on cylinder #6. I plugged in my Tech one, and the R Int is 146 with the L Int at 132. BLM is at 133 for both. Also, the O2 voltages were jumping around a lot.

Is the ticking/knocking noise likely the flywheel, and the overall problem likely the coil?

Thanks for all of your help.

[mike100]

put a metal tube (like an old brake line) on a stethoscope or to a rubber hose you can stick in one ear and run it along the exhaust flange and any welds that might be leaking on the exhaust system.

[XfireZ51]

A little more information would be helpful like, what year car, miles, mods, what side is the tick on, etc.

[Dmod81]

92, 56000 miles, headers w/ cats/3" exhaust/Haibeck chip. Coils and injectors were replaced (Accels) in about 08, about 7,000 miles ago. I can't hear it very well from the top of the car, but can hear it better from under. Seems louder on the drivers side, but that may just be the garage wall echoing.

I'll also use a stethoscope to see if there is an exhaust leak or if there is any discernable noise under the can cover today.

So is the no light from the timing light on the #6 cylinder not really a smoking gun then? It just seemed weird that it worked on all 7 of the other wires.

[XfireZ51]

The motor shake would suggest a miss. Which would be consistent with a cylinder not firing as indicated by the timing light. I'd swap the plugs between 4 and 6 and see if that changes at all. Also compare the color of the plugs to see if they look similar. And see what u get using the stethoscope as mike suggested.

[Dmod81]

OK, I'll do all of that after work. Thanks

[A26B]

Although the LT5 is a paired cylinder/waste spark ignition, bad spark on a single cylinder can and has occurred on more than one instance, and resolved by a coil replacement. That being said, the problem is probably related to a coil terminal, bad coil internal connection to the terminal or corrosion since a winding breakdown would affect both cylinders.

I have not experienced the "dry plug wire boot misfire to ground" that Marc Haibeck has diagnosed and resolved. Several others here on the forum have had the problem and fixed it using Marc's recommendation, liberal application of silicone di-electric grease in the boot.

In that same vein of thought, I heartily recommend and use silicone dielectric grease on all electrical terminals and the weather seals in the connectors whenever the opportunity presents.

So, as previously stated; (1) check the spark to ground. orange = weak, blue with 3/4" gap jump = good coil & wire, (2) good spark & good plug with misfire may = need to grease the plug boot (3) if still missing after (1) & (2) check ok, replace the coil. I always save the most difficult and costly possibility until last.

[USAFPILOT]

mouse got in mine once, caught with a sticky trap

[Dmod81]

Just ran the car in the dark, nothing seen. Last time I changed the plugs, I filled the boots with dielectric grease, but I don't know what's on the coil ends. I'm going to start the plenum removal tomorrow.

[RICHARD TILL]

I replaced my coils with MSD`S last year due to no spark on #3 cylinder only. A month later i was pulling the plenum again. I`ll never pull it again without cleaning the contacts inside the starter solenoid.